M Farooq,
M A Mian, F R Durrani and M
Syed

Abstract

Data were collected during the years
2000-2001 in Chakwal district; Pakistan to investigateegg production performance of 109 randomly selected flocks.

Average age at point-of-lay, and at
peak-of-lay, egg laying period, percent hen-day, and peak production and
hen-day, and hen-housed egg production were 126±1.02 days, 200±4.84days,
241±4.84 days, 69.3±0.51%, 92.1±0.34%, 205.±3.61 eggs and 185.±3.60 eggs,
respectively. Number of culled eggs per bird was 7.70±0.01, including 1.03±0.01% thin shell and 2.71±0.02%, broken eggs.
Age at point-of-lay (b=1.130; p<0.0009) and peak-of-lay (b=0.145; p<0.03) had a positive association with
mortality. Percent hen-day egg production was negatively associated with
age at point-of-lay (b=-0.11;
p<0.02) and mortality (b=‑0.32;
p<0.014). Hen-day egg production was negatively associated with age at
point-of-lay (b=‑0.40;
p<0.08), mortality (b=‑1.26;
p<0.028) and positively associated with percent hen-day egg production
(b=1.45; p<0.001).

Better egg production was found for; Hisex
strain of layer than Babcock, Nick-chick and Hyline;for large than small sized flocks; for layers
kept in cages than on floors; for flocks maintained at optimal stocking density
under better hygiene as compared to flocks maintained at a higher stocking rate
under poor hygiene.

Introduction

Eggs are the major business outputs in
commercial table egg production and the higher the egg production the better
will be the profit. Farooq et al (2001) found
positive association of egg production with net profit in broiler breeders and
reported major contribution of eggs in total returns. Verma
and Singh (1997) reported 87.3% contribution of eggs to total returns.Commercial egg type layers started laying
eggs at the age of 20-21 weeks and produced 277 eggs till 72nd week
of their production cycle according to Petek (1999).
North (1984) found 266 and 257 number of eggs as hen-day, and hen-housed egg
production during 52 weeks laying period for layers kept in cages.

Egg production is a dependent variable
and is influenced by several factors like strain of chicken, feeding,
mortality, culling, health and management practices, age at point-of-lay, and
peak lay and persistency of lay. North (1984), Petek
(1999) and Tolimir and Masic
(2000) observed variable egg production performance for various strains of
chicken. Adams and Craig (1985) reported a decrease in egg production with
increased stocking rate. Carey et al (1995) observed higher incidence of
cracked eggs in over-crowded houses as compared to optimal stocking rate. Akyildiz et al (1993), Tanaka (1993) and Kristensen and Silleb-Kristensen
(1996) reported that flocks having higher persistency of lay produced more eggs
than those with poor persistency. Housing system can also result in variability in performance of laying
hens. North (1984), Horne-Van and Van-Horne (1994) and Moorthy
et al (2000) found better egg production performance of layers reared in cages
than on deep litter (floor rearing).

The present study was undertaken to
document egg production parameters and study associated factors affecting egg
production performance of commercial laying hens in Chakwal
district, Pakistan.

Materials and methods

Data source and prediction of sample size

This study was undertaken during the
years 2000-2001 to investigate egg parameters and egg production performance of
commercial layers in Chakwal, Punjab, Pakistan.Sample size for the study was determined by calculating the coefficient of
variation from the data generated in the same area by Tariq
et al (2000). Maximum coefficient of variation observed for total eggs
production was selected as an index for estimating sample size to accommodate
both maximum and minimum values of variations in other production and economic
traits.

The following model, developed by Casely and Kumar (1989) was adopted
for determining sample size.

K2 * V2N
=-----------
D2

WhereN was sample size, K the normal deviation at 95%
confidence interval, V the coefficient of variation of the selected variable
andD the margin of error assumed to
be 0.1.

Measurements and data structure for statistical analysis

After determining the required sample
size, data were
collected from 109 randomly selected flocks. Factors studied were stocking
density, hen-housed, rearing system, cage vs. floor rearing of bird, hygienic
measures adopted, vaccination practice, daily mortality (if any) during egg laying period, age at point-of-lay, age at
peak-of-lay, daily egg production and
voluntary culling during growing and laying periods. Hygienic status of the farm was categorized as
good, average and poor on the basis of floor
and house construction, vicinity of the farm, distance between sheds or other
dwellings, housing conditions, all-in, all-out system, cleanliness and sanitation
of equipments/houses and disinfecting procedures / adopted. All farmers were
following standard vaccination and debeaking programs
advised by the chick suppliers.Stocking
rate of laying hens was assessed on the basis of number of chicks or birds/m2.
Deviation above or below the recommended level was grouped as over or under
utilization of the available space.

The effect of density of birds/m2,
hygienic condition of the farm, strain of chicken, flock size, cage vs. floor
rearing and system of housing on hen-day egg production of egg type layers
maintained in Chakwal was studied. The following
statistical model was constructed adopting the procedure of Steel and Torrie (1981):

Yijklmno
= ΅ + ai + bj
+ ck + dl+em+ fn+ (axb)ij+gijklmno

Where Yijklmno
was the response variable, ΅ the population constant common to all
observations, ai the effect of i-th hygienic condition on the farm (i=
poor, average and good), bj the effect
of j-th stocking rate in terms of birds/m2
area in the shed (j= more than required number of birds/m2, optimum
number of birds/m2 and less than required number of birds/m2),ck the effect of k-th rearing system (k = brood-grow-lay house, brood-grow and
lay house, brood and grow-lay house), dl the effect of l-th cage vs. floor rearing system (l= cage and floor), em the effect of m-th
flock size (m= small; ≤10,000, medium; >10,000<20,000
and large; >20,000), fn the effect of n-th
strain of chicken (n= Babcock, Nick-chick, Hyline and
Hisex), (axb)ij the interaction between i-th
hygienic condition and j-th density of birds/m2
and gijklmno the residual term associated with each Yijklmno,
normally, independently and identically distributed with mean zero and unit
variance.

A similar model was used to study the
effect of aforementioned variables on age at first and peak lay, peak and
hen-day lay, egg laying period and hen-housed egg production.

Association between various
parameters namely, mortality during egg laying period, voluntary culling, age
at first and peak lay, peak and hen-day lay, egg laying period and hen-day egg
production was worked out using the following regression model.

The coefficient of multiple
determinations "R2" was computed as follows,

R2
= (ry^y)2

Where R2 was the coefficient of multiple determination, ry^y  the correlation between predicted and
actual values. The coefficient R2 was
adjusted using the following definition:

R2
(adjusted) = [(n-1)R2 - k]/[n-k-1]

Where n was the number of
observations and kthe number of independent variables in the Model (Wonnacott
and Wonnacott 1985).

Results and
discussion

Age at point-of-lay and peak-of-lay

North (1984) and Singh and Belsare (1994) reported
higher age at point-of-lay and at peak-of- lay than the present findings (Table
1). Tolimir and Masic (2000) found
almost similar age at point-of-lay whereas Lai and Kan (2000) reported higher age at peak-of-lay than the present
findings. The findings of the present study suggest an earlier age at
point-of-lay and delayed age at peak-of-lay in laying hens maintained in Chakwal.

Table 1.
Egg production performance of commercial laying hens

Variables

Mean±SE

CV (%)

Age at
first-of-lay (days)

126±1.02

8.4

Age at
peak-of-lay (days)

200±0.22

8.2

Egg
laying period (days)

241±4.89

29.9

Peak
percent lay

92.1±0.34

3.8

Percent
Hen-day lay egg production

69.3±0.51

7.6

Hen-day
egg production (#)

205±3.61

17.5

Hen-housed egg production (#)

185±3.60

18.4

Culled
eggs (#)

7.70±0.01

33.2

Thin-shell eggs (%)

1.03±0.01

150.1

Broken
eggs (%)

2.71±0.02

187.6

Flock size, stocking rate and rearing system had no
significant effect on age at point-of-lay whereas, strain of the chicken and
hygienic conditions on farm had a significant effect. Layers kept in cages
attained peak-of-lay at lower age compared with those kept on the floor (Table 2). Hisex
layers had earlier age at point-of-lay and peak-of-lay than Babcock (Table 3).

abMeans with different subscripts in the
same row are different at a =
0.05.

Age at point-of lay
and peak-of-lay was higher (p<0.05)
in laying hens maintained under poor hygienic conditions than those under good
hygienic conditions (Table
4). The delay in age at point-of-lay under poor hygienic conditions is
attributable to higher mortality and stressful conditions that the laying hens were
exposed to. This was also evident from the positive association (b=1.13;
p<0.0009) of age at point-of-lay with mortality. Holding other independent variables constant, one percent unit increase in mortality
delayed age at point-of-lay by 1.13 days.Age at peak-of-lay was also found positively associated (b=0.14; p<0.03) with mortality, suggesting
that increase in mortality by one percent unit will increase age at peak-of-lay by
0.145days.

Table 3.Traits and egg production performance of
egg type laying hens as affected by strain of the chicken

Babcock

Nick-chick

Hyline

Hisex

Age at point-of-lay (days)

136a±0.74

133a±1.42

117b±1.00

116b±1.40

Age at peak-of-lay
(days)

204a±0.29

201b±0.46

200b±0.59

195b±0.59

Egg laying period
(days)

241a±4.86

242a±11.45

242a±11.2

241a±11.2

Peak percent lay

92.7a±0.40

93.5a±0.73

90.5b±1.03

91.8b±0.64

Percent hen-day
egg production

68.1b±0.63

68.7b±1.24

69.5ab±1.28

70.9a±1.30

Hen-day egg
production

200c±4.56

201c±4.32

206b±9.47

214a±8.25

Hen-housed egg
production

179c±4.56

181c±4.32

185b±9.47

195b±8.25

abc Means with different subscripts in the same row were
significantly different at a =
0.05

North (1984), Petek
(1999) and Kristensen and Sillebak-Kristensen
(1999) reported higher egg laying period (>52 weeks) than the present
findings (Table 1). The smaller egg laying period in the present study was
because of seasonal trends and higher fluctuations in egg prices. Price offered
for an egg in summer season was not even compensating the incurred cost on
individual eggs as consumption declines during summer season. Customarily
people prefer other livestock products like yogurt instead of eggs during
summer season. There are no proper processing and egg storage facilities in the
country that could provide better option to continue egg production in summer
season as well. The farmers usually tried to terminate egg production in summer
season and get new flocks in egg production at the end of summer season. Chicks
were usually procured from February through May and the same flock was disposed
off before May in the commencing year.

Flock size, stocking rate, strain of the chicken, rearing
system, cage vs. floor rearing and hygienic conditions on farm had no effect on
egg laying period. Egg laying period
was positively associated with percent hen-day production (b=2.84; p<0.0008),
age at peak-of-lay (b=2.01; p<0.007) but negatively associated with age at
point-of-lay (b=-2.07; p<0.001) and mortality (b=-0.545; p<0.1564).The adjusted R2 of the fitted
model was 31.4%. Holding other independent variables constant, a 1% unit increase in
percent hen-day egg production and one-day increase in age at peak-of-lay,
increased egg laying period by 2.84and 2.01days, respectively.On the other hand a 1% unit increase in mortality
and delay in age at point-of-lay by one day reduced egg laying period by
2.07and 0.54days, respectively.

Percent hen-day egg production

Akyildiz et al
(1993) reported lower percent hen-day egg production (67.3%), whereas Tanaka
(1993), Kristensen and Sillebak-Kristensen
(1996) and North (1984) found higher values (72.5, 74.5, 73%, respectively) than
the present findings. The smaller percent hen-day egg production in the present
study could be attributed to poor management and hygienic conditions on farms.
Percent hen-day egg production was negatively associated with age at point-of-lay(b=-0.11; p<0.02), age at peak-of-lay (b=-0.09; p<0.68) and mortality (b=‑0.31; p<0.014) but positively
associated with peak percent lay (b=0.13;
p<0.4). The adjusted R2 of the fitted model was 21.4%.
Holding other independent variables constant, a 1% unit increase in mortality,
delay in age at point-of-lay by one day and reduction of one percentage unit in peak percent lay, reduced percent hen-day
egg production by 0.11%, 0.091% and 0.32%,
respectively. An increase in percent hen-day egg production by 0.14% was
obtained with one percent unit increase in peak percent lay.

Flock size,
cage vs. floor rearing, hygienic conditions on the farm and stocking rate had a
significant effect (p<0.02) on percent hen-day egg production. Large sized
flocks were more persistent, having higher peak percent lay and percent hen-day
production than small sized flocks (Table 4). Laying hens maintained in cages
had higher peak percent lay and percent hen-day egg production than those kept
on floor (Table 2). Kumar and Mahalati (1998) and
Nair and Ghadoliya (2000) reported better egg-laying
performance in large than small sized flocks. Muthusamy
and Viswanathan (1998) and Petek
(1999) found higher egg laying performance of laying hens in cages than those
kept on floor. The higher percent hen-day egg production in large sized flocks
and hens kept in cages could be attributed to better management and rearing
environment.

Interaction of hygiene and stocking rate also
affected percent hen-day egg production. Poor hygiene coupled with higher
stocking rate significantly reduced hen-day lay. Layers maintained under poor
hygienic conditions had lower peak percent lay and percent hen-day egg
production than those under good hygienic conditions (Table 6). Laying hens
maintained at optimum stocking rate were more persistent in percent hen-day egg
production as compared to those at a higher stocking rate (Table 5). Probably,
laying hens maintained under poor hygiene in overcrowded houses were more
exposed to stress and polluted environment that could have caused deterioration
in their performance.

Table 4.Traits and egg production performance of egg
type layers as affected by flock size

Small
(<10,000)

Medium
(>10,000<20,000)

Large
(>20,000)

Age at point-of-lay
(days)

126a±1.35

126a±2.42

125a±1.96

Age at peak-of-lay
(days)

241a±0.30

240a±0.52

240a±1.88

Egg laying period
(days)

242a±6.63

241a±13.79

240a±0.26

Peak percent lay

90.8b±0.41

91.3b±0.89

94.3a±0.49

Percent hen-day egg
production

67.4b±0.71

68.7b±1.12

71.8a±0.37

Hen-day egg
production

202c±2.07

203b±10.35

211a±2.07

Hen-housed egg
production

182c±4.50

183b±10.35

190a±2.07

abc Means with different subscripts in the same row were
significantly different at a =
0.05

.Strain of the chicken and rearing system had a
significant on percent hen-day egg production. Although, Nick-chick had a
higher peak percent lay than Hisex, Hisex was more persistent in percent hen-day production
than Nick-chick (Table 3). Differences in percent hen-day egg production among
various strains of chicken were also reported by North (1984) and Lai and Kan (2000). Percent hen-day egg production was
significantly higher for laying hens in brood-grow and lay houses than those in
brood-grow-lay houses (Table 7).

abc Means with different subscripts in the same row were
significantly different at a =
0.05.

Hen-day and hen-housed egg production

North (1984) reported higher hen-housed and hen-day egg
production during 52 weeks of production period than the present findings. Hen-day
and hen-housed egg production in the present study was for 241 days (34.5 weeks)
compared with 52 weeks for the study reported by North (1984). Nevertheless, the
observed hen-day and hen-housed egg production could be considered higher as
there was a difference of71 eggs in about 117 days period.Hen-day egg production was negatively associated with age at
point-of-lay (b=‑0.40;
p<0.08), peak percent lay (b=‑0.066;
p<0.94) and mortality (b=‑1.26;
p<0.028) but positively associated with percent hen-day egg production
(b=1.45; p<0.001), laying period (b=0.47; p<0.53), peak percent lay
(b=0.61; p<0.42) and voluntary culling (b=0.33; p<0.71). Adjusted R2
of the fitted model was 67.2%. Findings of the present study suggested that
higher age at point-of-lay, peak percent lay and mortality reduced hen-day egg
production. On the other hand increase in percent hen-day egg production, egg laying period, peak percent lay and voluntary culling
resulted in an increase in hen-day egg production.

Flock size,
cage vs. floor rearing, strain of the chicken, stocking rate and hygienic
conditions on the farm had a significant effect on hen-day and hen-housed egg
production. Significantly higher hen-day, and hen-housed egg production was
obtained in large than small sized flocks (Table 6). Significant differences
were also found in hen-day and hen-housed egg production among laying hens
produced either in small or medium sized flocks. Ames and Ngemba (1986), Kumar and Mahalati
(1998), Nair and Ghadoliya (2000) and Farooq et al (2001) reported better egg production
performance in large than small sized flocks. Significantly higher hen-day and
hen-housed egg production was observed for egg laying hens kept in cages than
those kept on floor (Table 2). North (1984),Horne-Van and Van-Horne (1994), Muthusamy and Viswanathan (1998)
and Petek (1999) reported higher egg production of
layers in cages than those kept on the floor. The findings of the present study
suggested better management and appropriate rearing environment for layers in
large flocks kept in cages.

Table 6.Traits and egg production performance of
egg type layers as affected by hygienic conditions on farm

Poor

Average

Good

Age at
point-of-lay (days)

130a±1.68

124b±2.12

123b±1.34

Age at peak-of-lay
(days)

205a±0.36

198b±0.56

197b±0.28

Egg laying period
(days)

242a±9.00

242a±8.82

240a±6.56

Peak percent lay

90.1b±0.54

92.5a±0.62

93.6a±0.44

Percent hen-day
egg production

68.0b±0.89

69.4b±0.90

70.5a±0.77

Hen-day egg
production

197c±6.81

204b±5.91

215a±5.17

Hen-housed egg
production

175c±6.82

184b±5.90

196a±5.16

abc Means with different subscripts in the same row were
significantly different at a =
0.05.

Higher hen-day and hen-housed egg
production was found for Hisex than Babcock (Table
3). Differences in hen-day and hen-housed egg production for Nick-chick and
Babcock were also significant. North (1984), Petek
(1999) and Tolimir and Masic
(2000) also found strain differences in hen-day and hen-housed egg production.
Hen-day and hen-housed egg production was higher under brood-grow and lay
rearing system than under brood-grow-lay rearing system (Table 7).

Table 7.Traits and egg production performance of
egg type layers as affected by housing system

Brood-grow-lay

Brood-grow and lay

Brood and grow-lay

Age at first lay
(days)

126a±2.26

125a±1.57

126a±1.60

Age at peak lay
(days)

202a±0.68

197b±0.35

200a±0.35

Egg laying period
(days)

240a±10.59

241a±8.64

242a±5.77

Peak lay (%)

91.2a±0.63

92.9a±0.71

92.3a±0.63

Hen-day lay (%)

66.9b±0.63

72.4a±1.25

68.6b±1.25

Hen-day egg
production

195c±4.10

217a±7.85

204b±4.10

Hen-housed egg
production

176c±4.09

195a±7.85

184b±4.09

abc Means with different subscripts in the same row were
significantly different at a =
0.05

Significantly
higher hen-day and hen-housed egg production was found under good than that
under poor hygienic conditions on farm (Table 6). Differences in hen-day and
hen-housed egg production under poor and average hygienic conditions on farms
were also significant. . Significantly lower hen-day and hen-housed egg
production was found at lower stocking than at optimal stocking rate (Table 5).
Non-significant differences were found in hen-day egg production at higher or
lower stocking rate. Adams and Craig (1985) and Carey et al(1995) also reported poor egg
production performance of egg laying hens at a higher stocking rate. Interactionsbetween
hygienic conditions on farm and stocking density of birds also had a
significant influence on hen-day and hen-housed egg production. Considering both
qualitative variables as dummies in the model after defining hen-day egg
production as function of hygiene and stocking density, a decline in hen-day
egg production was found with increased stocking rate and hygiene approaching
poor from good.

Culled eggs

Incidence of broken eggs was higher on floor than in layers
kept in cages (Table 2).Adams and Craig
(1985) and Carey et al (1995) also found higher incidence of broken eggs in floor-reared
laying hens than those kept in cages. The higher proportion of culled eggs on
floor rearing could be attributed to poor management.

Conclusions and recommendations

Age at point of lay was lower than most of the reported
research findings.

Better egg production was found for;

Hisex strain of layer than Babcock, Nick-chick and Hyline

large than small sized flocks

layers kept in cages than on floors

layers reared in brood-grow and lay houses

flocks maintained at optimal stocking density under better
hygiene as compared to flocks maintained at a higher stocking rate under poor
hygiene.

Higher stocking density coupled with poor hygiene had
adverse effects on egg production performance. Maintaining larger flocks in
brood-grow and lay houses under good hygiene and use of cages instead of floor
housing will improve egg production performance of laying hens in Chakwal district.

References

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Akyildiz A R, Konca Y, Ceylan N,Ciftci I and Corduk M 1993 Effects of using barley and/or sorghum in
diets on the performance of caged laying hens. AnkaraUniversitesiZiraatFakultesiYilligi. 43(1-2): 85-95.

Petek M 1999 Production traits
and economic efficiencies of different Genotypes oflayers reared by enterprises in Bursa province and its
near vicinity. VeterinerFakultesiDergisiUludagUniversitesi. 18(1-2): 65-77.